Portland cement is one of the most widely used materials in the construction industry. Although unmodified concrete and cement mortar systems (i.e., those not containing a polymer latex modifier) have adequate properties for many construction applications, there remain many areas in which such properties, particularly strength, and adhesion to cementitious substrates are not acceptable. The addition of styrene-butadiene polymer latexes to portland cement have provided compositions having improved strength, flexibility and adhesion to cementitious substrates. The present invention is directed to cement additives based on certain styrene-acrylate interpolymeric latexes which additives provide portland cement compositions having significantly improved strength and adhesion to cemmentitious substrates as compared to cement compositions containing the prior known styrene-butadiene latex modifiers.